Radio repeater



H. E GoLDsTINE 2,344,813

m19' REPEATER Filed V sept. 26. 1941 Fly. /f

mmf com/erm AMM 00" 430m s zsmc. amm GMO/Q INVENTOR A Mmm s. Gowsm/E ATTORNEY Patented Mar. 21, 1944 OFFICE lRADIO REPEATER Hallan E. Goldstine, Rocky Point, N. Y., assigner to Radio VCorporation' of America, a corporation of Delaware Application September 26, 1941, Serial No. 412,401 8 Claims. (Cl. Z50-15)'- The present invention relates to radio repeater systems and, more particularly, to a means for controlling the operating frequencies of the radio links in said system.

An object of the present invention is the provision of a radio repeater station having an accurately controlled output frequency.

Another object of the present invention is the provision of a repeater station in which the incoming frequency is converted to a lower frequency for amplification and reconverted to a high frequency for retransmission. A further object of the present invention is the provision of a repeater station, as aforesaid, which requires only a single accurately controlled 4oscillator forthe required frequency conversions.

Another object of the present invention is the provision of a repeater station, as aforesaid, in which a change of oscillator frequency has very little effect in the frequency of retransmission.

Still another object of the present invention is the provision of a relay station which does not require careful balancing of the circuits therein.

Still another object of the present invention is the provision of a relay station which does not require extremely highly selective circuits therein for its operation.

Still a further object is the provision of a relay station requiring a minimum amount of auxiliary equipment such as oscillation generators, multiplying stages, etc.

The foregoing objects, and others which may appear from the following detailed description, are attained by the provisionof a relay station having a single source of high frequency oscillations which is used at the input of the station to change the received signals to an intermediate frequency and at the output to change the intermediate frequency to the frequency of retransmission. In the intermediate frequency system the frequency is shifted by an amount equal to the difference between the receiving and transmitting` frequencies. The amount of this frequency shift is a high percentage of the intermediate frequency and is, therefore, easily carried out.

The invention will be more fully understood by reference to the following detailed description, which is accompanied by a drawing in which Figure 1 illustrates an embodiment of the present invention and Figure 2 illustrates a modification thereof. I

Referring, now, to Figure 1, incoming lsignals are received on a directional receiving antenna II directed toward the immediately preceding relay station of the system. An operating frequency of 500 megacycles has been assumed, for the sake of illustration, but other frequencies may be used if desired. The received signals may be amplified, if necessary, and then are applied toa converter I2. Locally generated oscillations at a frequency of 400 megacycles, for example, from oscillator I4 are also applied to the converter I2. The 400 megacycle oscillator I4 maybe either a line controlled or stabilized oscillator or -it may be controlled from a 4crystal oscillator source. It should preferably have an output of from' 2 to 3 Watts though onlya small amount of this energy is used in the converter I2 for converting the incoming signal. The resultant outputfrom converter I2 at a first intermediate frequency of 100 megacycles is applied to a further converter and amplifier I6. Locally generated oscillations at a frequency of 20 megacycles are applied to converter IE from oscillator I8. The frequency of the oscillations generated by oscillator IBis controlled by a crystal control circuit I9. The output from converter and amplifier I E is, in the example chosen, at a second intermediate frequency of megacycles. The second intermediate frequency, further amplified if necessary,v is appliedv to a converter 20 where it is mixed with the output from oscillator I4 and converted to the output frequency of 480 megacycles which is ra- 'diated by directive antenna 22 directed toward the next relay station of the system.

It will be noted that the first conversion in the station requires only a small amount of energy from oscillator I4 and the remainder is used for high level conversion in converter 20. Y

In the foregoing description the frequencies used were used only as an illustration and it may, under some circumstances, be more economical from `the. power standpoint to use a higher intermediate frequency so that the oscillator frequency generated by oscillator I4 may be lower and the oscillator, therefore, may be more eicient. y

An advantage of the system so far described is that no extra filtering for the selection of side bands in the converter is necessary because the intermediate frequency amplifiers in converter and amplifier. I6 have suflicient selectivity to readily reject the upper side ,band or the carrier, as desired.

'I'he modification shown in Figure 2 is the same as that of Figure 1 las far as `the receiving, converting and retransmitting of energy is concerned and the elements used, therefore, have the same reference characters.

However, in this modification only a single cs cillator I8 controlled by crystal i9 is used. The output of oscillator i8 is applied to converter I6, as in the previously described embodiment but, in addition thereto, the output is also applied to a chain o ffrequency multipliers 23. The output of multipliers 23` Ais applied to oscillator 2d to control its 400 megacycle output for the input and output frequency conversion.

It will be noted that in the invention as described there is required no separation of frequencies at small percentage spacings. Inthe intermedaite frequency system the intermediate frequency is shifted by an amount equal vto the difference between the received and transmitted frequencies. This frequency shift is a relatively high percentage of the intermediate frequency and, consequently, is easy to carry out. In the modification shown in Figure 2 only a single crystal oscillator is used to control both the lower frequency for the intermediate conversion and for the high frequency heterodyning power sources. yOnly about half as much equipment is needed to supply heterodyning currents as is required -by previously known relay systems, of which I am aware.

It should further be noted that in an arrangement constructed according to the present invention the outgoing frequency is essentially independent of any change in frequency of the local oscillator vand the only change that would be present would be a percentage change due to either the megacycle crystal frequency chang-r ing' slightly. The following numerical example illustrates this fact:

. If the crystal or oscillator .frequency of the embodiment of Figure 2 should change 50 kilocycles at 20 megacycles or .25% (a large change for a crystal) the 400 megacycle output of 24 would then change to 401 and the first intermediate frequency to 99, then the second intermediate frequency would be 99-20.05=78.95 kiiocycles and when this is heterodyned with 4011 megacycles the output frequency will be in this case 479.95 orgaof thepercent frequency change of the '20 megacycles, or .0122%. If a V-cut crystalI was used and the frequency change was 1 part'per million per degree centigrade and it is assumed that the variation is 100 parts per million or .01% variation then the output frequency would only vary el; of that, or .00`042%.

When

:frequency difference between intermediate frequencies fin=input frequency faut-:output frequency Af=change in frequency of oscillators i 8, i9.

,distinctly understood that my ,invention .is not 75 limited thereto but that modifications within the scope of my invention may be made.

Iclaim:

1. In a radio relay station having input and output circuits operating at different frequencies, a frequency converter in each of said circuits, means for supplying a single high frequency Wave to both of said converters, an inA termediate frequency channel connecting said input and output circuits and means in said channel for shifting the intermediate frequency by an amount equal to the difference between the input and output frequencies.

2. In a radio relay station having input and output circuits operating at different frequencies, a frequency converter in each of said circuits, means for supplying a single high frequency wave to both of said converters, an intermediate frequency channel connecting said input and output circuits and means in said channel for shifting the kintermediate frequency by an amount equal to the difference between the input and output frequencies, said means including a frequency converter and a high frequency oscillator coupled thereto.

3. In a radio relay station having input and output circuits operating at different frequencies, a frequency converter in each of said circuits, means for supplying a single high frequency wave to both of said converters, an intermediate frequency'channel connecting said input and output circuits and means in said channel for shifting the intermediate frequency by an amount equal to the difference between the input and output frequencies, said means including a converter and a crystal controlled high frequency oscillator coupled thereto.

4. In a radio relay station having input and output circuits operating at different frequencies, a frequency converter in each of said circuits, means for supplying a single high frequency wave to both of said converters, an intermediate frequency channel connecting said input and output circuits and means in said channel for shifting the intermediate frequency by an amount equal to the difference between the input and output frequencies, said means including a frequency converter and a high frequency oscillator coupled thereto, said source of high frequency energy and said high lfrequency oscillator being controlled by a single frequency standard.

5. In a radio relay station having input and output circuits operating at different frequencies, a frequency, converter in each of said circuits, means for supplying a single high frequency wave to both of said converters, an intermediate frequency channel connecting said input and output circuits and means in said channel for shifting the intermediate frequency by an amount equal to the difference between the input and output frequencies, said means including a frequency converter and a high frequency oscillator coupled thereto, and means for multiplying the frequency of oscillations generated by said high frequency oscillator tc the frequency of said high frequency source and means for utilizing said multiplied frequency oscil'lations to control the frequency of operation of said high frequency source.

6. A radio system including input and output circuits operativeon different frequencies, frequency converter means for converting signals applied to said input circuit to an intermediate frequency, frequency converter means for converting signals at another intermediate frequency to the frequency of said output circuit, means for applying a single high frequency wave to both of said converters, a source of oscillations having a frequency equal to the diiference between the frequencies of operation of the input and output circuits and converter means energized from said source for converting the first of said intermediate frequencies to the other of said intermediate frequencies.

7. A radio system including input and output circuits operative on different frequencies, frequency converter means for converting signals applied to said input circuit to an intermediate frequency, frequency converter means for con verting signals at another intermediate frequency to the frequency of said output circuit, means for applying a single high frequency Wave to both of said converters, a source of oscillations having a frequency equal to the difference between the frequencies of operation of the input and output circuits and converter means energized from said source for converting the first of said intermediate frequencies to the other of said intermediate frequencies, the frequency of said high frequency Wave being continuously related to the frequency of said source of oscillations by a constant.

8. A radio system including input and output circuits operative on different frequencies, frequency converter means for converting signals applied to said input circuit to an intermediate frequency, frequency converter means for converting signals at another intermediate frequency to the frequency of said output circuit, means for applying a single high frequency wave to both of said converters, a source of oscillations having a frequency equal to the difference between the frequencies of operation of the in-l put and output circuits and converter means en-, ergized from said source for converting the first'` of said intermediate frequencies to the other of said intermediate frequencies, said high frequency wave being a multiple of the output from said source of oscillations.

HALLAN E. GOLDSTINE. 

